"A few years ago I went to Spain for the first time, and like many I was surprised by how late is dinner," Maggiolo writes on his blog. "The first night I dined almost alone in a restaurant at 8 p.m., going away just as people were starting to come in. Of course this can be mostly explained by cultural reasons, but the clearly later-than-usual summer sunsets must also have played a role in shaping the Spanish days."

Maggiolo, an engineer at Google, color-coded a map of the world, showing locations where the clock is behind the solar day in red and places where it is ahead of the solar day in green. The more ahead or behind, the deeper the color.

More than70 countries now observe Daylight Saving Time, but the beginning and ending dates often differ from the U.S., which has itself changed the schedule a number of times over the years.

The Energy Policy Act of 2005 extended the dates of Daylight Saving Time by about a month to its current schedule in 2007, starting on the second Sunday in March and ending on the first Sunday in November.